Unlike a typical walkthrough, we will not be holding your hand for every action, but rather give you general advice and for individual missions, give you specific tips on tricky situations.
The tips here will not be applicable to the expansions as the AI uses different tactics.
The missions were mostly played on Normal. On harder difficulties, generally the enemy will be harder to kill and you will probably need stronger units or a higher unit ratio to overcome their advantage.
- Projection of Firepower
- Any army is basically about the projection of firepower. You want to hit the enemy from as far as you can and without them hitting back.
- Hand-to-hand or other close-combat assault forces can win, but they are also a lot more micromanagement. When you start having 3 or more units you can get traffic jams and some units will just stop and idle, apparently having timed out on movement orders because they can't find a path to the target location due to being blocked by the units in front.
- In a "real life situation", having some strong hand-to-hand troops is essential to block the enemy shock-trooping your units with them.
- This is because there is the possibility of friendly fire. In Warhammer 40K, you do NOT have full friendly fire rules. Your Space Marines can safely fire pretty much anything they want into a melee and you won't hit your own units. (There *is* friendly fire when it comes to artillery, however).
- Also, the AI generally just goes for the nearest enemy unit, so you can bait them into directing all their attention on that one unit, which just has to survive long enough for you to rain concentrated firepower on them. Which is why you want a LOT of ranged units that can shoot at anyone you want, instead of a bunch of melee units that can only fight when they are in contact with an enemy model.
- You won't have every unit at the start, and depending on the terrain you may not want to field everything because of traffic jams, but in general you will want to...
- Send Scouts ahead to locate the enemy.
- Hit them with Whirlwind artillery fire, unreliable as it is. 2-4 whirlwinds is generally a good number. The AI does not generally attempt to locate the source of attacks originating from the fog of war.
- Intercept anything approaching your Whirlwinds with long range fire such as missile launchers from space marine squads, or long-range weapons on Dreadnoughts or Terminators. Use tanks if you can't get anything else but they are very prone to traffic jams.
- Intercept anyone who gets closer with concentrated ranged fire.
- Fight hand-to-hand as a last resort. If you build a unit specifically for hand-to-hand, you are using up your troop and/or vehicle cap with a unit that may forever be in reserve.
- Fighting on more than one front
- Don't do it. Sometimes things happen very quickly and if you are flipping back and forth you may be too late to set Reinforcement on overwatch for a unit, or to pull them out of being overwhelmed.
- When you are attacked from multiple directions, hold ground and build turrets to cover your position so that, preferably, you can hold the position with just turrets alone and for a long time. Then, move your assault force to advance and hold more ground. A single, strong, and mobile assault force is better than spreading your force too much and leaving units scattered around to defend your territory.
- Identify the battle front. You will still want to protect your strategic locations with Listening posts and 1-2 turrets each (against teleported-in enemies), but in general, once you have eliminated your blind spots and cleared the enemy from them, you can focus on advancing the battle front. Knowing where your enemy is not is just as important as knowing where he is.
- Utterly invaluable. If they come across a lonely strategic point they might as well capture it. Otherwise they are really just spotters.
- Do not reinforce Scout units to more than 2 units since they aren't meant to fight and you can only get 2 sniping rifles.
- Sniping rifles will be the only attack you want to use, and only if you are sure the scouts are not going to be detected while firing from the enemy's fog of war. It takes a heck of a long time to kill anything this way, but the range and firing from the fog of war makes it viable to kill the odd target now and again.
- Do not click movement target locations too close to a capturable point such as a Critical Location. The scouts will immediately drop their Infiltration invisibility.
- When you have a lot of troops, you may need to manually move them or they get stuck behind other troops and go idle. A unit of infantry occupies its own space and has space in between. Automatically path-ed movement won't overlap infantry, but you can by choosing a single unit and using the green move arrow to direct them. They can in this way be made to overlap into another units.
- Having a lot of units may also mean that some units will not simply follow the ones in front if they are all going to the same place. They may calculate those units as obstacles and start going the long way around, through dangerous or unexplored territory if necessary. Keep an eye on your minimap for units headed the wrong way.
- If the enemy is in cover and you can move in without coming under fire from too many other units, you might as well move your attacking unit into the same cover. That way you will both have the benefit of cover.
- Typically if you run directly away from the enemy, you cannot return fire. Instead, try to retreat from shooting enemies in a sideways manner, and heading for cover. That way, you can still fire back.
- Wherever you are, look for a good fallback position, such as Heavy Cover or one of your own listening posts (preferably upgraded and additionally defended by turrets).
- To force a unit to keep moving instead of stopping to attack, use the green move arrow (hotkey "V"). They will still attack if something comes in range, but won't stop for anything.
- Build these early and often to keep the enemy tangled up on the battle front. Enemies generally have attack-move orders (they stop to attack whatever is in range) instead of just-move orders where they are going to a specific location and won't linger to attack.
- Turrets don't count against your squad or vehicle caps. Visit them with your builder gangs to repair them if necessary, but if you have enough of them around a Listening Post, that generally won't be an issue.
- Missile launcher upgrades have longer range and can shoot targets in the fog of war. Although they are slower than anti-infantry turrets against infantry, they have a knock-down and knock-back effect against infantry.
Specific Mission Tips
Mission 1 - Planet Fall
The mission babysits you through this tutorial. Nothing special here except to note that events are scripted to trigger when you get close, and generally do not play themselves out while you are busy elsewhere.
Mission 2 - Infiltration
A nice, linear map.
If you don't want to do the Scouting way or if you fail it by losing your scouts, the mission does not fail. Instead, the Captain will take over the mission, but without scouts.
Once you establish the base, hold the southeast side and clear the way you came first since you've already mapped it out.
Mission 3 - Under Siege
You come under fire from vehicles who can spot your infantry before you can spot them. Keeping scouts/lookouts ahead of you is definitely key, as is outfitting your space marines with as many missile launchers as they can have to take down ork armour as quickly as possible and from as safe a distance as possible.
Mission 4 - Destroy the Xenos
Early on you will encounter some enemies on a ridge. There's a message about using Rhinos but ignore that. Instead, use scouts to find them, missiles from your space marine squads to clear them, then assault marines to fly over and capture the strategic point there. Afterwards, you can probably delete the assault marines to make room in your troop cap for something else if you really need it.
This is probably the most annoying mission because that Gargantuan Squiggoth can probably flatten your entire army, or lay waste to enough of it for any remaining orks to overwhelm you. Fortunately, it is scripted to return to protect the main ork base, so if you flee all your units enough you can save it for last. Be careful of the traffic jam possible at the corridor leading to the ork base.
Slowly scout the base, pounding everything with Whirlwinds. Clean it out until the final plateau with the ork boss and orkamungus. A small, mobile force with scouts and space marines standing far enough off to just use missile launchers might be all you need initially. Bring in the Whirlwinds later.
Pound everything with Whirlwinds, including the Sqiggoth and the ork boss Orkamungus. Try to clear all buildings if possible, then weaken the orkamungus, then clear it too.
Mission 5 - A New Lead
Eldar teleport and can pop out of nowhere, but it is still not really necessary to have very strong hand-to-hand units. Maybe just one unit, but your space marines are generally hardy enough that you can survive a unit long enough for the rest to shoot the enemy to death.
They don't try to get behind your front line yet. Not until the next mission.
Mission 6 - Into the Maw
Once you've reached the Gate, some Eldar will pop in far behind to try to take some strategic points, so fortify them with turrets before you get too far.
Mission 7 - Sacrifice
The Avatar is essentially a hand-to-hand unit, so whichever unit it is chasing should be manually controlled. Don't use attack-move, just plain movement (big green arrow). Units will still attack if possible, but won't stop to engage. In this way, lead the Avatar to a bunch of turrets around a listening post and let it get shot to death. Do the same with the Bloodthirster in Mission 10.
Instead of retreating, if you are feeling bold and have anti-vehicle weapons on your units, you can let them do the shooting while you lead it around with the one unit it is chasing.
Mission 8 - The Chapel
The steps of the chapel have a mess of units that are best handled by drawing them out or pounding them down with Whirlwinds. Scouting is key, either with regular scouts or the skulls from listening posts. On Normal you can fight it out, but casualties are typically very high.
Once you reach the Chapel doors, if you want to look around and clear the map (not really necessary), you can work on the doors right away. Any anti-vehicle weapon will do, including missile Turrets. Tanks not required. If you build turrets near the Requisition points, they will immediately attack the door and once that is down a swarm of enemies will come out, so know what you're getting into and get ready.
Mission 9 - Unholy Ceremony
The Guardsmen here are actually not pushovers IF you get them grenade launchers as soon as possible. The mess of them can hold ground quite easily since the enemy typically sends only one unit of anything to capture or recapture strategic points. You may also want to consider NOT reinforcing their numbers too much so that the smaller, more maneuverable squads can be positioned more quickly to focus their long-range grenade fire.
At the start, grab strategic points but don't enter the inner area where you can come under fire from listening posts and too many Chaos forces at the same time. Instead, sit your Guards at each Listening Post until you've fortified it with 3-4 turrets and possibly a Leman Russ tank (you get them free periodically -- they all start out as neutral units in disrepair and slowly get repaired and ready for action)..
When the Captain appears in the southeast, you will ideally have your western forces easily holding their positions so you can focus on fortifying the Captain's position. Upgrade his Terminators then start your attack.
At this point, I moved the captain up north until he reached the Guardsmen there. This way, if I needed to suddenly help one force with the other, there would be no terrain surprises delaying things. After that, just the Captain's force was enough to clean out just about the entire map.
The minimal win condition is to hold the relics long enough, if you don't want to grind the enemy down.
Mission 10 - Old Friend
The Bloodthirster is near the Relic location that is near your starting base, and it can chase you all the way back to your base, so be sure your base is already fortified before you draw it's attention.
The rest of the map is just the usual take-and-hold.
Mission 11 - All Out War
The demon lord more or less stays near the Chaos base slightly northeast of the map centre, and won't chase you too far, so if you flee far enough it will leave. It will not retreat if you are within its pursuit radius, so if it is chasing one unit, move that unit constantly and have the rest attack it with anti-vehicle weapons. The initial batch of Space Marines, fully upgraded with 4 missile launchers per squad, can kill the demon lord in this way on "Impossible" difficulty. You do not have to clear the map, only to kill the demon lord.
The Eldar allies basically send a stream of units to try to capture the northern relic and eventually get beaten back to their base. If they run out of units and resource, they will go idle and can't even try to capture any strategic points. If you reach their position and capture all strategic points (e.g., because they were captured by Chaos units), then they may also go idle once they run out of resources as they can't use yours and won't try to capture yours.
Draw the Demon Lord to a bunch of turrets if possible, but otherwise just mass a bunch of heavy anti-vehicle units and slowly beat it down. Nothing too special here, and an easy mission even on Impossible difficulty.